1. Field of the Invention
The present invention generally relates to an optical information recording and reproducing device for recording information on a recording medium, for example, an optical disk, with a laser beam generated from a light source.
2. Description of the Related Art
The CDs and CD-ROMs for music, and recently, reproduction-only media (recording medium) such as DVD-ROMs, and information reproducing devices are put to practical use with the spread of multimedia. Furthermore, recently, phase change type media, besides a write once optical disk using pigment media, and an erasable type magneto optical (MO) disk using MO media, have also gained attention, and information recording and reproducing devices utilizing such recording medium are being put to practical use. The erasable type DVD media has become the center of attention as multimedia-recording media and as mass storage media of the next generation.
The phase change type media record information by reversibly phase changing the recording material to a crystal phase and an amorphous phase. Furthermore, the phase change type media can record and reproduce information with only a laser beam generated from a light source, which consists of a semiconductor laser and does not need an external magnetic field as with the MO media. The phase-change media also allow an overwrite recording in which recording and erasing of the information are performed simultaneously by the laser beam.
A semiconductor laser emission waveform of a single pulse generated based on, for example, a 8-16 modulation code is given as a general recording waveform for recording information on phase change type media. However, in a single pulse recording using such recording waveform, problems in that recording marks may produce tear-shaped distortions due to heat reserve, formation of the amorphous phase may be insufficient due to insufficient cooling speed, and recording marks having low reflection to the laser beam may not be obtainable, may arise.
The above problems are prevented by forming marks on the phase change type media using a laser beam of multi-pulse shape, which uses multi-stage recording power, as shown in FIG. 10, as a recording method, in which information is recorded on the phase change type medium of a DVD system. The mark portion of the multi-pulse shape consists of a leading heating pulse A for sufficiently pre-heating the recording film of the phase change type medium to above its melting point, a plurality of trailing consecutive heating pulse B, a consecutive cooling pulse C in between pulse A and pulse B, and a final cooling pulse Cr. If the light emission power (peak power) of the leading heating pulse A and the heating pulse B is referred to as Pw, the light emission power (bias power) of the cooling pulse C and Cr as Pb, and the reproducing power as Pr, respective light emission powers are defined as
Pw greater than Pb≈Prxe2x80x83xe2x80x83(1).
Furthermore, the space portion of the multi-pulse shape consists of an erasing pulse D and its light emission power (erase power) Pe is defined as
xe2x80x83Pw greater than Pe greater than Pbxe2x80x83xe2x80x83(2).
In this way, by assuming the recording waveform as the multi-pulse light emitting waveform, an amorphous phase is formed during the mark portion of the phase change type medium because of the quenching condition of heatingxe2x86x92cooling by the heating pulse A, B, and the cooling pulse C, Cr. On the other hand, a crystal phase is formed during the space portion because of the slow cooling condition of only heating with the erasing pulse D. Thus, a sufficient difference in reflectance is obtained between the amorphous phase and the crystal phase.
Moreover, when recording information on a pigment medium of the DVD system, recording marks cannot be produced due to heat reserve in the single pulse recording, and thus, a recording method of forming marks with a laser beam having a multi-pulse shape as shown in FIG. 11 is proposed. In FIG. 11, if the light emission power (peak power) of the leading heating pulse A and the heating pulse B is referred to as Pw, the light emission power (bias power) of the cooling pulse C and the space portion D as Pb, and the reproducing power as Pr, respective light emission powers are defined as
xe2x80x83Pw greater than Pb≈Prxe2x80x83xe2x80x83(3).
In the early stages of CD-ROM or DVD-ROM, a CLV (Constant Linear Velocity) type method enabling large storage capacity had been common as a velocity control method of a spindle motor, but in order to make the rotational speed of the spindle motor faster to increase the information transfer speed, it became necessary to simplify the control of the motor, and thus a CAV (Constant Angular Velocity) control type method, in which the angular speed of rotation is constant, became effective.
Since the CD media, and the DVD media have the same information recording density throughout the entire region on the assumption that both media are reproduced in the CLV type method, when recording of CAV type recording is carried out to a media of such structure, the linear velocity of recording (recording linear velocity) is faster towards the outer circumference. Accordingly, when recording is carried out with the same optical pulse emission for both the inner and the outer circumference, the laser power may become insufficient on the side of the outer circumference. Furthermore, when recording using a medium optimized for CLV recording, a good recording cannot be performed if the linear velocity is too fast or too slow, and malfunctions resulting in deterioration of overwrite properties and increase of jitters may occur.
In order to solve such problems, pulses having a slightly shorter input pulses are emitted instead of the multi-pulse if the relative speed of the information recording medium and the laser beam is faster as disclosed in, for example, Japanese Laid-Open Patent Application No. 6-12674. Furthermore, in a Japanese Laid-Open Patent Application No. 5-274678, if the laser beam is irradiated to a region on the outer circumference side, the duty ratio of the pulse emission is larger than that in irradiating a region on the inner circumference side.
Since pulse widths are set according to the radial position and the recording linear velocity as shown in the conventional art, in for example, Japanese Patent No. 02982556, a register is provided for correcting pulse widths, and the light emitting pulse shape is determined based on the value of this pulse width setting register in a pulse shape generating circuit. The value of the register may be varied according to the radial position or the recording linear velocity.
Furthermore, in a Japanese Laid-Open Patent Application No. 7-272275, two types of PLL clock and laser driving current setting registers are provided as techniques for updating the light emitting level according to the linear velocity; and by selecting the PLL clock and the laser driving current setting register alternately every time a zone is changed, recording may be performed consecutively to different zones.
In the recording operation using the CAV control type method, it is necessary to update the pulse width or the light emitting level registers, but generally, the output values of the registers tend to be in an unsteady state at the instant the contents of the registers are updated, and when at least a pulse is emitted based on a register value at this instant, an abnormal emission such as glitches may occur and damage the medium. Furthermore, if a sequence operation is performed based on the register value when the pulse shape generating circuit generates the pulse shape, the sequence operation may fail if the register value is an abnormal value, and all subsequent generating pulses may become abnormal pulses.
Although the method of alternately changing the registers as described in a Japanese Laid-Open Patent Application No. 7-272275 is effective for solving the above problems, in Japanese Laid-Open Patent Application No. 7-272275, the laser driving current register is changed for every zone and because the boundary of the zones is not a data recording region, the behavior of the light emitting waveform at the instant of change (changing instant) is not particularly considered. When the pulse width setting register or the driving current setting register of the peak level is changed during the period of the multi-pulse emission, an abnormal emission of, for example, glitches may occur at the changing instant.
The general object of the present invention is to solve the above described problems and prevent abnormal light emission even when the pulse width or laser driving current setting registers are updated during the recording operation, and to prevent the pulse width setting sequence from becoming an abnormal operation and damaging the medium.
The above object of the present invention is achieved in that the optical information recording and reproducing device has a plurality of pulse width setting registers for setting pulse width of the multi-pulse emissions, that the pulse width setting register is changed and then the recording operation is performed when updating the pulse width of multi-pulse emission, and that at a time of changing the pulse width setting register during recording, generation of the recording pulse train is stopped.
The above object of the present invention is further achieved in that a period for stopping the generation of the recording pulse train is during space data recording.
The above object of the present invention is further achieved in that the optical information recording and reproducing device has a plurality of laser driving current setting registers for setting an amount of laser driving current of each light emitting level, and that the laser driving current setting register is changed and then a recording operation is performed when updating the amount of laser driving current, and a time to change the laser driving current setting register for setting the amount of current driven by light emission power for forming mark data is within the space data output period.
The above object of the present invention is further achieved in that the optical information recording and reproducing device has a plurality of laser driving current setting registers for setting an amount of laser driving current of each light emitting level; and that the laser driving current setting register is changed and then recording operation is performed when updating the amount of laser driving current, and a time to change the laser driving current setting register for setting the amount of current driven by light emission power for forming space data is within the mark data output period.
The above object of the present invention is further achieved in that mark/space information is recorded, erased, and reproduced on a phase change type recording medium by laser power of three values of bias level/erase level/peak level.
The above object of the present invention is further achieved in that a time to change the pulse width setting register and/or the laser driving current setting register is during a recording period of longer than a predetermined length.
The above object of the present invention is further achieved in that the pulse width setting register and/or the laser driving setting register is included in a laser driving arrangement for driving the laser.
The above object of the present invention is. further achieved in that the pulse width setting register is set according to a change in the channel clock cycle.
The above object of the present invention is further achieved in that the recording is performed in a CAV control method at a constant rotating angular speed.